Wireless direction-finder



Tm. 14,- 1958 SHIGEO sATo 2,820,219

- WIRELESS DIRECTION-FINDER Filed July 15, 1953 V I 2 Sheets-Sheet 1 J0saw-awe INVENTOR.

/ ATTORNEYS Jan. 14, 1958 sHl'e'EdsATo; 2,820,219

WIRELESS-DIRECTION-FINDER Filed July 13, 1953 2 Sheets-Sheet z 32 W0 roeINVENTOR.

ATTORNEYS.

Patented Jan. 14, 1953 2,820,219 WIRELESS DIRECTION-FINDER Shigeo Sato,Tokyo-to, Japan Application July 13, 1953, Serial No. 367,569 7 Claims.(Cl. 343-118) This invention relates to an improved wirelessdirection-finder.

In the usual wireless direction-finder provided with a cathode-ray tubeand capable of indicating directly all directions of the electric wavereceived, it is customary to indicate the intensity and direction of theelectric wave on the cathode-ray tube by rotating the directionalantenna at a proper speed, making the tube describe a circular orring-shaped fluorescent image at a speed synchronous to said rotationand modulating the image by the wave obtained by amplifying the electricwave received.

The method for describing a circular or ring-shaped fluorescent image onthe cathode-ray tube may comprise transforming a single phase A. C.voltage into two phase A. C. voltage by means of a phase converter andsupplying the output voltage of said converter to the vertical andhorizontal deflecting plates or deflecting coils. The method asdescribed above, however, has the disadvantagesthat it is very difficultto make a phase converter having good frequency characteristics and toobtain sufficient two phase power, the latter defect being due to highimpedance.

On the other hand, it is well-known to rotate the deflecting coils ofthe cathode-ray tube at a speed synchronous to the rotation of thedirectional antenna by means of a selsyn motor. This system, however,has the disadvantages that the image is distorted due to nonsynchronismand that vibration and noises occur in the apparatus which drives thedeflecting coils.

It has been proposed to couple the polyphase A. C. generator directlywith the directional antenna to' eliminate the defects as describedabove. According to such method, however, the generated voltage isconstant and brightness modulation of the cathode-ray tube is carriedout only by the variation of the output voltage in the antenna, so thatthe fluorescent image corresponding to the minimum sensibility of thedirectional antenna is very indistinct resulting in very difiiicult andinaccurate observation.

The object of this invention, therefore, is to provide adirection-finder which is relatively simple in construction and accuratein operation and has no defects as described above.

The above object and other objects of this invention are accomplished bya system which comprises a directional input device and a rotary typepolyphase A. C. generator capable of generating polyphase voltages whichvary in relation to the output voltage of the input device, thepolyphase voltages being used as the deflectingelements of thecathode-ray tube and the input device and generator being revolvedsynchronously with respect to each other under their directly couplingcondition.

This invention will be more clearly understood by reference to thefollowing detailed description taken in conlug drawings, wherein:

Fig. 1 shows a schematic arrangement of an example of this invention.

Fig. 2 is a connection diagram of an example of a rotary type two phaseA. C. generator to be used in the JllCCtlOIl-fiIlClBI' of thisinvention.

Fig. 3 is a connection diagram of an example of the exciting circuit forfeeding the two phase A. C. generator illustrated in Fig. 2.

Fig. 4 is a schematic view of a fluorescent image obtained by theapparatus illustrated in Fig. 1.

Fig. 5 shows a schematic arrangement of another example of thisinvention.

Fig. 6 is a schematic view of a fluorescent image obtained by theapparatus illustrated in Fig. 5.

Referring to the example illustrated in Fig. l, the directional inputdevice 1 consists of a loop antenna, Ad-

.cock type antenna or poniometer which is coupled directly with twophase A. C. generator 2. The motor 3 is arranged to rotatesynchronously, with both parts 1 and 2, at a speed of about tenrevolutions per second. The generator 2 and cathode-ray tube 4 areconnected electrically so that the first phase output of said generatormay be supplied to a pair of deflecting plates of tube 4, V

and the second phase output may be supplied to another pair ofdeflecting plates, the latter pair being positioned perpendicularly tothe former pair. A receiver 5 is connected to the output terminals ofthe directional input device 1 and a Wave detector 6 is connected to theoutput terminals of the receiver. An oscillator '7 capable of generatingan oscillating voltage of about 20 kilocycles per second is connected tothe output side of detector 6 so that the output voltage of theoscillator may be superposed to the detected output voltage of saiddetector, the resultant output voltage being supplied to the two phaseA. C. generator 2 after amplification by an amplifier Couplingtransformers 9 are inserted in the circuits connecting the generator 2and the cathode-ray tube 4 to make the impedances in the secondarywinding of said generator 2 match with the resultant of the impedancesin the deflecting plate circuit of the cathode-ray tube and theconnecting wires Ill. Any type and construction of the generator may beadopted if it is a rotary type, because it must be coupled with thedirectional input device to effectuate the principle of this invention.

For example, a generator similar to the ususal two phase A. C. generatorof large capacity may be used, but such type is very complex inconstruction and is inaccurate in operation due to unbalance of theconnecting terminals and due to mutual inductance and stray capacitancein the part of said terminals.

The generator illustrated in Fig. 2, however, is very simple inconstruction and manufacture and is capable of generating efficientlyand accurately a two phase A. C. voltage output.

The two phase A. C. generator illustrated in Fig. 2 consists of a statorA consisting of a circular ring-shaped iron core 11 and an endlesswinding 12 wound toroidally with a uniform distribution on the core, anda rotor B consisting of an iron core 15 and a winding 16 similar tothose of the stator A. Iron cores having a cross sectional surface ofany form, for example, rectangular, circular or any other form may beused, but it is preferable to form it from a material such as dust core,which is relatively low in high frequency loss and large inpermeability. The stator winding 12 is provided with vertical terminals13 and horizontal terminals 14, the former being led from two points ona diametrical vertical-line of said winding and the latter being ledfrom two points on a diametrical horizontal-line of said winding. Therotor B ,is supported rotatably in the stator A by a suitable means forexample, by holding it between two disks supported rigidly by a rotaryshaft, the disks and rotary shaft being omitted. in the drawing.

For the purpose of concentric support of the stator and rotor any othermeans may be adopted.

The endless winding 16 wound toroidally with a uniform distribution onthe rotor iron core is connected to the slip rings 17 at its bisectedpoints as shown in Fig. 2.

In the generator illustrated in Fig. 2, when the rotor is revolved at aconstant speed and any A. C. voltage of a suitable high frequency issupplied on the winding 16, then two phase A. C. voltage will occur atthe terminals 13 and 14 due to an induction phenomenon between thestator A and the rotor B. The large part of magnetic path of saidgenerator consists of the iron cores 11 and 15 of large permeability andonly very little air gap is left between said iron cores, so that themutual inductance between both windings 12 and 16 becomes very large.For the purpose of increasing said mutual inductance more effectively,it is preferable to wind the windings in the slots of their iron cores.Moreover, the stator and rotor windings of said generator are woundtoroidally with a unifrom distribution on their cores under endlesscondition, so that said generator is very simple in construction and hasno unbalanced constructional parts such as the connection ends of thewindings, such parts taking no part in voltage induction. Furthermore,there are no large stray inductance and stray capacitance, so that anaccurate two phase A. C. voltage will be generated effectively. When thestator winding 12 is wound with a uniform distribution and the rotorwinding 16 is wound with a sine distribution, then two phase A. C.voltage of great accuracy will be obtained. In the embodiment of thegenerator illustrated in Fig. 2, it may be allowable to use the statorand rotor of same size and to fix them concentrically on a rotary shaftside by side instead of the concentric arrangement as indicated in Fig.2.

Fig. 3 shows an actual connecton diagram of the oscillating circuitcapable of generating an exciting voltage to be supplied to the A. C.generator. In the Fig. 3, the voltage e corresponds to the carrieroutput voltages of the receiver 5 in Fig. 1, for example, to the outputvoltage of an intermediate frequency which is obtained by demodulatingthe voltage induced in the directional input device by a superheterodynereceiver. It is provided with a detecting vacuum tube 18, a load 19 anda filter 20. The filter is made so as to eliminate the carrier wavecontained in the amplified output voltage of the directional inputdevice and pass only the envelope of the carrier'wave therethrough, thefrequency of said envelope corresponding to the fundamental frequencydue to rotation of the directional input device.

The exciting voltage 2 of about 20 kilocycles is superposed on theoutput voltage of the filter 2t) and through transformer 21 and avoltage divider 22. The resultant voltage is supplied to the gridelectrode of the vacuum tube amplifier 23. For amplifier 23 it ispreferable to use, for example, a 6817 tube, in which the mutualconductance varies suddenly in accordance with the variation of the gridvoltage.

In the secondary circuit of the output transformer 24 is connected acondenser C to form a resonant circuit to attenuate the harmonic waves.All parts in the apparatus of Fig. 3 should be designed so that when theoutput voltage of the receiver is almost zero the output power of theoutput transformer 24 may becomes maximum and decreases with theincrease of the output power of the receiver. For example, theparameters should be selected so that when the voltage of the load 19decreases below 5 volts due to increase of the output power of thereceiver, the mutual conductance of the amplifier 23 (6817 tube) becomeszero, and also the output power of the transformer 24 becomes almostzero.

The operation of the direction-finder as described above will beunderstood by the following descript on.

The apparatus illustrated in Fig. 1 is provided with a loop antenna (notshown). When a l1ne normal to the surface of said antenna is set to thedirection of the line connecting two diagonal points of the rotorwinding in the two phase A. C. generator, the direction of the lineconnecting two diagonal points of the stator winding and the directionof a pair of deflecting plates in the cathode-ray tube are set to thestandard direction, for example, to north pole, the first pair of outputterminals of the two phase A. C. generator is connected with a pair ofdeflecting plates in the cathode-ray tube and the second pair of saidterminals is connected with another pair of deflecting plates and theantenna is coupled directly with the generator and rotated together withthe latter by a synchronous motor at a speed of about ten revolutionsper second, then the rotor winding of said generator will be suppliedwith an exciting voltage of about 20 kilocycles per second and modulatedby the output voltage of the directional input device, and in the statorWinding will be induced two phase A. C. voltage corresponding to themodulated voltage, so that a fluorescent image as indicated in Fig. 4will be seen on the cathoderay tube.

As will be understood from Fig. 4, when the output power of the antennais zero, the exciting voltage of the generator becomes maximum and thelocus thereof takes a form similar to a circle as indicated by brokenline 29. However, upon appearance of the output power in the antenna theexciting voltage decreases in inverse proportion to the magnitude of theoutput power, so that an envelope 25 of leaf-shaped fluorescent imagewill appear as a locus of maximum deflecting position of electron beamcapable of oscillating symmetrical to the center point 26. In thegeneral cathode-ray tube, however, the diameter of electron beam isabout 0.5 mm. and the residual fluorescence of electron beam is onlyabout 0.1 second, so that when a wave of about 20 kilocycles is used andthe antenna is revolved at a speed of about ten revolutions per second,the striped pattern 27 will be scarcely visible. When the direction ofthe deflecting plates in the cathode-ray tube is set to the standarddirection, it is possible to decide the direction of the electric wavereceived by the antenna by means of measuring the angle 0 between thepeak points 28 of the envelope 25 and said standard direction. The widthof the envelope 25 may be decreased by increasing the amplificationcoefficient of the receiver, and the radius of the locus '29 may bevaried by the voltage divider 22 as indicated in Fig. 3.

The apparatus illustrated in Fig. 5 consists of a directional inputdevice 30, a two phase A. C. generator 31, a motor 32, a cathode-raytube 33, a receiver 34, coupling transformers 35 and a frequency changer36 including an amplifier and functions similar to the apparatusillustrated in Fig. 1. The frequency changer 36 is of a type which iscapable of transforming the carrier wave, which carries the electricwave received by the receiver 34, into an exciting wave sufiicientlystrong and stable, the frequency thereof being about 20 kilocycles.Therefore, the output power of the two phase A. C. generator 31, whichis supplied with said exciting voltage, becomes zero when the outputpower of the directional input device 30 is almost zero and on the otherhand it becomes an almost constant value when the output power of thedirectional input device increases up to a value over a certain value.As a result, when any output power of the directional input device 30occurs due to an incoming electric wave, a circular envelope 37 having acenter point 38 will appear in the cathode-ray tube as indicated in Fig.6. In this example also striped pattern 39 will appear. The pattern asabove, however, can "be made invisible by adopting the exciting voltageof about 2t) kilocycles and by rotating the directional input device ata speed of about ten revolutions per second. On the other hand,wedge-shaped gaps 40 will appear at the positions corresponding to zerooutput of the directional input device, said positions corresponding tothe peak points 28 in Fig. 4.

It is possible, therefore, to measure accurately the angle deflectedfrom the standard direction, that is, the emitted direction of thecoming electric wave. Moreover, it is possible to make the widths of thegaps 40 very narrow by increasing the amplitude of the output of thefrequency changer 36.

In the above examples, a cathode-ray tube provided with deflectingplates is used. However, one provided with deflecting coils may be usedwith similar excellent results. Furthermore, it is within the scope ofthis in vention to use any other polyphase A. C. generator, for example,three phase A. C. generator instead of a two phase A. C. generator, butin this case a cathode-ray tube provided with deflecting devicecorresponding to said polyphase should be adopted to make the operationsimilar.

As will be clear from the above description, the direction-finder ofthis invention has advantages in that the construction is relativelysimple, and A. C. generator and directional input device do not get outof synchronism because of the rotary type of said generator and of theirdirect coupling resulting in lack of errors due to distortion of thefluorescent image. Moreover, noises would not occur as in the case ofrevolution of the deflection coil.

Furthermore, as the voltage induced in the polyphase A. C. generatorvaries in relation to the output of the direction antenna, thefluorescent image is very clear and observation becomes very easy andaccurate.

Since it is obvious that many changes and modifications can be made inthe above described details without departing from the nature and spiritof this invention, it is to be understood that this invention is notrestricted except as set forth in the appended claims.

I claim:

1. A direction finder comprising, in combination, a directional antenna,a motor connected to said antenna to rotate the same and thereby tosweep its directional pattern, a generator having a ring-shaped statorcore and a ring-shaped rotor core, a toroidal exciting winding on one ofsaid cores and a two-phase toroidal output winding on the other of saidcores, said cores and windings being inductively related to one another,a direct mechanical connection between said motor and said rotor coreand its winding for rotation of the latter synchronously with therotation of said antenna, a cathode-ray tube indicator provided withorthogonally disposed deflection control elements, circuits connectingthe respective control elements to the respective phase outputs of saidoutput winding, a signal receiver connected for energization from saidantenna, and means connecting the signal output of said receiver to saidexciting winding whereby the twophase output of said generator iscontrolled in amplitude by the output signal strength of said receiver.

2. A direction finder in accordance with claim 1, said apparatus beingarranged so that the amplitude of the two-phase output of said generatordecreases with increasing signal strength output of said antenna, toprovide a leaf-shaped pattern on said tube having clear maximal points.

3. A direction finder in accordance with claim 1, in which said meanscomprises: a detector connected to the output of said receiver, anoscillator, and means for superimposing the outputs of said detector andsaid oscillator upon said exciting winding.

4. A direction finder in accordance with claim 1, in which said meanscomprises a frequency changer connected between said exciting windingand the output of said receiver.

5. A direction finder in accordance with claim 1, in which said meanscomprises: a detector connected to the output of said receiver, anoscillator, and means for superimposing the outputs of said detector andsaid oscillator upon said exciting winding, said oscillator beingadjusted relative to the tuning of said receiver to provide a compositesignal to said exciting winding which is ap proximately of the value of20 kilocycles per second.

6. A direction finder in accordance with claim 1, in which one of saidtoroidal windings has a uniform spatial distribution along itscorresponding core, and in which the other of said toroidal windings hasa sinusoidal spatial distribution along its core.

7. A direction finder in accordance with claim 1, said apparatus beingconstructed and arranged so that the output voltage of said generator issubstantially zero when the signal output of said antenna isapproximately zero, and so that the output voltage approaches a maximumlimiting value for increasing values of antenna signal, to provide clearwedge-shaped gaps in the circular image on said tube.

References Cited in the file of this patent UNITED STATES PATENTS2,403,967 Busignies July 16, 1946 2,409,456 Tolson et al Oct. 15, 19462,427,905 Fyler Sept. 23, 1947 2,483,399 Burroughs Oct. 4, 19492,485,585 Goldstein Oct. 25, 1949 2,656.536 Lockhart Oct. 20, 1953FOREIGN PATENTS 894,379 France Mar. 13, 1944 51,645 France Dec. 10, 1942

